E. Hargreaves 



310 



at this stage two layers of chitin are to be distinguished, one being that 

 which originally enclosed the fourth instar, the other, inside this, which 

 is destined to be the adult skeleton (Fig. 36). This may be called an 



Fig. 36. Section through head of fourth instar. 



internal moult. The eyes, from being mere spots in the young pupa, 

 grow enormously to form the compound eyes of the imago. The body 

 grows very much in thickness, becoming box-hke in the older pupa 

 (Fig. 27). Also, the antennae, legs and wings may be seen curled up 

 inside the outer case, but outside the body of the insect. As is the 

 case in the preceding stages, the new legs and antennae are formed 

 inside the old ones, and since those of the imago are much longer than 

 those of the pupa, they become folded as they grow. The claws and 

 second tarsal segment easily fill one of the pupal legs (Fig. 37). The 



Fig. 37. Adult leg developing in pupa. 



wings are outgrowths of the inner layer of chitin, the growth being 

 continuous and gradual and thus differing from that which takes place 

 at successive moults, in steps as it were, in some other insects. So far 

 as I can make out, the wings arise as evaginations, and not as invagi- 

 nations, which are later evaginated as in insects like the Lepidoptera. 



